This application is based on Japanese Patent Applications HEI 11-275981, filed on Sep. 29, 1999 and 2000-73030, filed on Mar. 15, 2000, the entire contents of which are incorporated herein by reference.
a) Field of the Invention
The present invention relates to a pulse tube refrigerator, and more particularly to a pulse tube refrigerator with improved housing structures for regenerating material or the like. The pulse tube refrigerator is used with precise physical and chemical apparatuses such as an NMR and an electron microscope.
b) Description of the Related Art
Ultra low temperature refrigerators such as pulse tube refrigerators are widely used for maintaining a low temperature environment for precise physical and chemical apparatuses such as an NMR and an electron microscope.
FIG. 7 is a cross sectional view showing the main part of a conventional pulse tube refrigerator 1. The pulse tube refrigerator 1 has: a compressor 2; a valve unit 3 for switching between high and low pressures; a high temperature end block 4; a low temperature end block (cooling end block) 5; a regenerator 6; a pulse tube 7; a flow rectifier 8 at a regenerator low temperature end; a flow rectifier 9 at a pulse tube low temperature end; and a flow rectifier 10 at a pulse tube high temperature end.
The high temperature end block 4 has a working gas supply port 11 and a working gas reciprocal port 12. Working gas or fluid such as helium gas is pulsatively supplied from the working gas supply port 11, via the inside of a supply port space 13, and to the regenerator 6. A buffer tank 15 is coupled to the working gas reciprocal port 12. An orifice 14 is provided in the working gas reciprocal port 12. The high temperature end block 4 is mounted on a mount flange 16 with mount bolts 17.
The regenerators is constituted of a regenerator case 18 disposed between the high temperature block 4 (mount flange 16) and the low temperature end block 5, and a. regenerating material 19 housed in the regenerator case 18. As the regenerating material 19, copper material, stainless steel material, metal fibers or punching metal is used. The regenerator 19 is filled in the regenerator case 18 at a predetermined density. While the working gas passes through the inside of the regenerator 6, regeneration is performed between the working gas and regenerating material 19 to cool the regenerating material 19.
The low temperature end block 5 is disposed facing the high temperature end block 4 at a predetermined distance. The regenerator 6 and pulse tube 7 are disposed generally in parallel between the low temperature end block 5 and high temperature end block 4. A commuter space 20 is formed in the low temperature end block 5 to make the lower temperature end of a gas passage in the regenerator 6 communicate with the low temperature end of the gas passage in the pulse tube 7. In the commuter space 20, the flow rectifier 8 at the regenerator low temperature end is disposed in a space 21 on the regenerator 6 side, and the flow rectifier 9 at the pulse tube low temperature end is disposed in a space 22 on the pulse tube 7 side.
The flow rectifier 8 at the regenerator low temperature side is made of flow rectifying material 23 (first flow rectifying material) filled in the space 21. The flow rectifier 9 at the pulse tube low temperature side is made of flow rectifying material 24 (second flow rectifying material) filled in the space 22.
The high temperature end of the pulse tube 7 communicates with the working gas reciprocal port 12 via the flow rectifier 10 at the pulse tube high temperature end.
The flow rectifier 10 at the pulse tube high temperature end is made of flow rectifying material 26 (third flow rectifying material) filled in a space 25 formed in the high temperature end block 4.
The flow rectifying materials 23, 24 and 26 are, for example, metal meshes or punching metal.
The working gas is pulsatively supplied into the regenerator 6 via the working gas supply port 11 and supply port space 13. This working gas is also supplied into the pulse tube 7 via the flow rectifier 8, commuter space 20 and flow rectifier 9. The pressure and volume of the working gas in the pulse tube 7 are changed. The flow rectifiers 9 and 10 rectify the working gas flow in the pulse tube 7. The phases of the pressure change and volume change are controlled by the orifice 14 and buffer tank 15. Heat is absorbed in the low temperature end block 5.
In the conventional pulse tube refrigerator 1, the regenerating material 19 is directly filled in the regenerator case 18. Similarly, the flow rectifying material 23 is directly filled in the regenerator side space 21, the flow rectifying material 24 is directly filled in the pulse tube side space 22, and the flow rectifying material 26 is directly filled in the orifice side space 25.
During the operation of the pulse tube refrigerator 1, if impurities such as water contents and other fluids are solidified, the regenerating material 19 or flow rectifying material 23, 24 or 26 may be clogged with the impurities. In such a case, the cooling performance may be lowered. In order to recover the original cooling performance, the temperature of the clogged areas are raised to remove solidified fluid contents.
However, if impurities are oil or the like flowed from the compressor 2, these impurities are difficult to be removed by raising the temperature of the clogged areas. In this cases it is necessary to replace the regenerating material 19 or flow rectifying material 23, 24 or 26 by new one.
In order to replace the regenerating material 19 or flow rectifying material 23, 24 or 26, it is necessary to stop the operation of a precise physical and chemical apparatus (cooling object) cooled with the pulse tube refrigerator 1 and raise the temperature thereof. This operation stop and temperature rise lower a running efficiency of the apparatus. In addition, a cooling operation is again required after material replacement, which results in a large cost and work and a long work time.
Furthermore, since the regenerating material 19 and flow rectifying materials 23, 24 and 26 are directly filled in the spaces, a replacement work itself is neither simple nor efficient.
Another type of a conventional pulse tube refrigerator has a structure that a flow rectifier (not shown) for communicating the working gas supply port 11 with the high temperature end of the regenerator 6 is provided by directly filling flow rectifying material (fourth flow rectifying material) in the supply port space 13 of the high temperature end block 4. Also with this pulse tube refrigerator having such a structure, a replacement work for flow rectifying material is not simple and a maintenance efficiency is lowered.
It is an object of the present invention to provide a pulse tube refrigerator capable of cold maintenance without an operation stop and temperature rise of a precise physical and chemical apparatus, by using a cartridge type regenerator and cartridge type flow rectifiers easy to be replaced.
It is another object of the present invention to provide a pulse tube refrigerator capable of easily replacing a clogged regenerating material or flow rectifying material.
According one aspect of the present invention, there is provided a pulse tube refrigerator comprising: a first pulse tube, a high temperature end and a low temperature end being defined at both ends thereof, and having an inner space; a first regenerator case of a tubular type, a high temperature end and a low temperature end being defined at both sides thereof; a first regenerator including a first cartridge case and a first regenerating material filled in the first cartridge case, the first cartridge case being removably inserted into said first regenerator case; a first passage communicating a space in said first regenerator case on a low temperature end side into which case said first regenerator is inserted, with a space in said first pulse tube on a low temperature end side; a gas supply unit for repeating a supply and a recovery of a working gas; and a second passage for coupling said gas supply unit to a space in said first regenerator case on a high temperature end side into which case said first regenerator is inserted.
Since the first regenerator can be removably mounted, the first regenerating material can be easily exchanged when the first regenerating material is clogged.
According another aspect of the present invention, there is provided a maintenance method for a pulse tube refrigerator having: a pulse tube, a high temperature end and a low temperature end being defined at both ends thereof, and having an inner space; a regenerator case of a tubular type, a high temperature end and a low temperature end being defined at both ends thereof; a regenerator including a cartridge case and a regenerating material filled in the cartridge case, the cartridge case being removably inserted into the regenerator case; a first passage communicating a space in the regenerator case on a low temperature end side into which case the regenerator is inserted, with a space in the pulse tube on a low temperature end side; a gas supply unit for repeating a supply and a recovery of a working gas; and a second path for coupling the gas supply unit to a space in the regenerator case on a high temperature end side into which case the regenerator is inserted, the method comprising the steps of: stopping an operation of the pulse tube refrigerator; covering the high temperature end of the regenerator case with a glove box so as to prevent atmospheric air from entering the space in the regenerator case even if the high temperature side of the regenerator case is opened, and preparing a new regenerator in the glove box; pulling the regenerator out of the regenerator case; and inserting the new regenerator into the regenerator case.
Since the high temperature end of the regenerator case is covered with a glove box even if the regenerator is dismounted, atmospheric air will not enter the inside of the regenerator case. Therefore, the regenerator can be replaced by a new one without raising the temperature at the low temperature end.